Television camera tube having channel multiplier surrounding electron gun

ABSTRACT

A television camera type tube including a target and an electron gun for producing an electron beam to scan the target. The scanning beam causes a return beam to be produced. A channel-type secondary electron multiplier is located near the gun end of the tube to receive electrons in response to the electrons moving in the return beam.

United States Patent 1191 1111 3,716,738

Beeli 1451 Feb. 13, 1973 4] TELEVISION CAMERA TUBE HAVING JCOhIHSOH "I CHANNEL MULTIPLIER a 3,440,470 4/1969 Decker ..313/103 SURROUNDING ELECTRON GUN 3,555,345 1/1971 Collings ..313/103 x Inventor: Johann Battesta Beeli, Sylmar, Calif.

International Telephone and Telegraph Corporation, New York, NY.

Filed: April 26, 1971 Appl. No.: 137,636

Related U.S. Application Data Continuation-impart of Ser. No. 850,749, Aug. 18, 1969, abandoned.

Assignee:

U.S. Cl. 3l3/65 R, 313/105 Int. Cl ..H0lj 31/28, H0lj 31/32, HOlj 43/24 Field of Search ..313/65, 65 A, 66, 67, 68, 94, 313/95, 102, 103, 104, 105

[56] References Cited UNITED STATES PATENTS 2,161,620 6/1939 Famsworth ..3l3/82 X Primary Examiner-Robert Segal Attorney-C. Cornell Remsen, Jr., Walter J. Baum, I

Paul W. Hemminger, Charles L. Johnson, Jr. and Thomas E. Kristofferson [57] ABSTRACT A television camera type tube including a target and an electron gun for producing an electron beam to scan the target. The scanning beam causes a return beam to be produced. A channel-type secondary electron multiplier is located near the gun end of the tube to receive electrons in response to the electrons moving in the return beam.

4 Claims, 3 Drawing Figures PAFENTEWWW 3,716,738

INVENTOR JOhA/VA/ 5. 5664/ TELEVISION CAMERA TUBE HAVING CHANNEL MULTIPLIER SURROUNDING ELECTRON GUN This application is a continuation-in-part of copending application Ser. No. 850,749 filed on Aug. 18, 1969, by J. B. Beeli for a TELEVISION CAMERA OR THE LIKE and now abandoned. The benefit of the filing date of said application, therefore, is claimed for this application.

BACKGROUND OF THE INVENTION This invention relates to electron multipliers and, more particularly, to a secondary electron multiplier for a television camera type tube.

The device of the present invention may be used in television camera tubes or the like, including, but not limited to, vidicons, image orthicons, plumbicons, cinticons, etc.

In the past, it has been the practice to employ a television camera tube including a target. and an electron gun to produce an electron beam to scan the target. An electron beam is then generated which returns toward the gun. Dynodes are placed near the gun in the shape of fixed sets of turbine fan blades. The dynodes produce an increase in the number of return beam electrons by a secondary electron emission.

The prior art dynodes have a gain limiting effect on the tube. Further, the dynodes are very small and are, thus, difficult and expensive to manufacture and to assemble.

SUMMARY OF THE INVENTION In accordance with the device of the present invention, the above-described and other disadvantages of the prior art are overcome by positioning a channeltype secondary electron multiplier near the electron gun of a television camera type tube to provide an increased return beam output to a collector electrode. The present invention may, thus, increase the tube gain by as much as a factor of l,000 to 10,000. At the same time, the channel-type multiplier substantially reduces manufacturing and assembly expense and difficulty. It also makes the tube more rugged against vibrations.

The above-described and other advantages of the invention will be better understood from the following description when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a longitudinal sectional view of a television camera type tube; and

FIG. 2 is a longitudinal sectional view of an electron multiplier which may be used in accordance with the device of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, atelevision camera type tube is indicated at 10. Tube may, for example, be an image orthicon.

Tube 10 has an evacuated envelope 11, a photocathode l2 fixed to one end thereof, and an electron gun 13 fixed in the center of envelope 11. Electron gun 13 is disposed at one end of envelope 11 opposite the end where photocathode 12 is positioned. An electron multiplier 14 is positioned adjacent photocathode 12. A target 15 is positioned adjacent multiplier 14. A field mesh 16 is positioned adjacent target 15.

Electrostatic deflection plates are positioned adjacent field mesh 16. A hollow, cylindrical, focus electrode 18 is positioned concentrically in envelope 11 between gun 13 and deflection plates 17. Four deflection plates 17 may be employed, although only two are shown.

Electron gunl3 is positioned in envelope ll inside a hole 19 in an electron multiplier 20. Electron gun 13 includes electrodes 21 and 22, a cathode 23, and a cathode heater 24.

A collector 25 is located in envelope 11 behind multiplier 20 to receive electrons therefrom.

Multipliers 14 and 20 may be entirely conventional except that the location of multiplier 20 is new, and the hole 19 therethrough is new. Still further, it is new to use two multipliers in image orthicons of the structure shown in FIG. 2. Except for hole 19, multiplier 20 may have a glass plate 26 with holes 27 therethrough. The surfaces of holes 27 may support secondary emission. Plate 26 has electrodes 28 and 29 evaporated thereon with holes 30 and 31 in registration with hole 27.

As stated previously, the construction of multipliers 14 and 20, as shown in FIG. 2, may be identical and conventional. However, it is only these structures, per se, which are conventional, and not their use in the tube 10.

The entire tube 10 may be conventional except for multiplier 20 in combination with electron gun l3. Electrode 21 has a hole 32 through which electrons are emitted and accelerated along a path 33. After striking target 15, these electrons follow along a path 34 and strike electrode 21 and cause electrons to be driven into multiplier 20. The surface of electrode 21 may support secondary emission.

As is now designed, the holes 27 through multipliers 14 and 20 are much smaller than the hole 19.

Typical operating voltages for the tube 10 are as follows:

Photocathode 12 l ,200 volts Multiplier 14 (input electrode) 1 ,000 volts Multiplier 14 (output electrode) 500 volts Target 15 +40 volts Field mesh 16 +800 volts Electrode 18 volts Electrode 21 +400 volts Multiplier 20 (input electrode) +600 volts Multiplier 20 (output electrode) +l .600 volts Collector 25 H ,800 volts Electrode 22 60 volts Cathode 23 0 volts In the prior art, an electron multiplier was located at the position of multiplier 20. The prior art multiplier consisted of several sets of fan blades similar to fixed turbine fans. The multiplier 20 provides substantial advantages over the prior art, in particular, the use of the channel-type electron multiplier 20 makes it possible to increase the gain of tube 10 by as much as a factor of 1,000 to 10,000. At the same time, multiplier 20 substantially reduces manufacturing and assembly expenses and difficulty.

The external surface of the cone 21 must be at an acute angle less than 78 for proper electron distribution to multiplier 20. It is preferably about 45.

Multiplier need not be provided with a hole for electrode 21. Electrode 21 may be located in front of multiplier 20 between it and electrode 18.

What is claimed is:

1. A television camera-type tube comprising: an evacuated envelope; a target fixed within said envelope at one end thereof; an axially positioned electron gun fixed within said envelope at the other end thereof, said gun being constructed to produce an electron beam to scan said target, said beam returning toward said gun away from said target; a perforated glass plate channeltype electron multiplier positioned adjacent and surrounding said gun to receive electrons from said return beam; said gun having a frusto-conical, secondary emissive, electrode surface of angle less than 78 in the path of said return beam directing electrons therefrom toward the input side of said electron multiplier; and a collector fixed within said envelope in a position on the output side of said multiplier to collect electrons therefrom, said collector being positioned on the opposite side of said multiplier from said target, said multiplier including a dielectric plate having a plurality of holes extending completely therethrough from said input side to said output side, said holes being defined by surrounding surfaces, said surfaces having a secondary emission ration greater than unity, a conductive input electrode having a plurality of holes extending completely therethrough, said input electrode being fixed relative to said plate inside said envelope in a position such that said input electrode holes lie in registration with said plate holes, a conductive output electrode having a plurality of holes extending completely therethrough, said output electrode being fixed relative to said plate inside said envelope in a position such that said output electrode holes lie in registration with said plate holes and said input electrode holes.

2. The invention as defined in claim 1, wherein said envelope is substantially cylindrical, said target being disposed perpendicular to the axis of said envelope, said electrode external frusto-conical surface pointing toward said target on the target side thereof and having an axis the same as that of said envelope, the conical surface being inclined at an acute angle of about 45 from saidaxis, said multiplier having front and rear surfaces parallel to said target, said front surface being closer to said target than said rear surface, said multiplier having a central hole therethrough large in comparison to said perforations, said gun being located in said hole, said frusto-conical surface projecting closer to said target than the said surfaces of said multiplier, said multiplier having first and, second electrodes evaporated. into said front and rear surfaces, respectively, said collector being a grid parallel to said surfaces spaced from said multiplier electrodes, said collector being positioned adjacent said second electrode, means for maintaining said first and second electrodes and said collector at successively higher potentials, said gun including a'cathode, and means for maintaining said cathode at a potential lower than that of said first electrode,

3. The invention as defined in claim 1, including a photocathode at said one end of said envelope on the side of said target opposite said electron gun, a second channel type electron multiplier between said target and photocathode, and means for deflecting and focusing said electron beam in the plane of said target.

4. The invention as defined in claim 1, wherein said gun includes a cylindrical electrode with a conical nose closing one end thereof except for a hole through the extreme point in the nose, said nose hole being small in comparison to the maximum cross-sectional dimension of said cylindrical electrode, said nose reducing in cross-sectional size in a direction toward said target, said plate input and output sides being approximately flat and parallel, said target being approximately flat and parallel to said input and output sides of said plate, means to direct said beam through said nose hole in a direction approximately perpendicular to the planes of said plate sides from a position on one side of said nose hole opposite that on which said target is located, said plate having an access hole approximately through the center thereof, said cylindrical electrode being located in said access hole, said nose being located closer to said target than said input electrode, said tube being constructed to cause said return beam to bombard the outer conical surface of said nose, said outer conical surface being adapted to support secondary emission responsive to said bombardment and to supply secondary electrons so created to the holes in said plate opening on the said input side thereof; 

1. A television camera-type tube comprising: an evacuated envelope; a target fixed within said envelope at one end thereof; an axially positioned electron gun fixed within said envelope at the other end thereof, said gun being constructed to produce an electron beam to scan said target, said beam returning toward said gun away from said target; a perforated glass plate channel-type electron multiplier positioned adjacent and surrounding said gUn to receive electrons from said return beam; said gun having a frusto-conical, secondary-emissive, electrode surface of angle less than 78* in the path of said return beam directing electrons therefrom toward the input side of said electron multiplier; and a collector fixed within said envelope in a position on the output side of said multiplier to collect electrons therefrom, said collector being positioned on the opposite side of said multiplier from said target, said multiplier including a dielectric plate having a plurality of holes extending completely therethrough from said input side to said output side, said holes being defined by surrounding surfaces, said surfaces having a secondary emission ration greater than unity, a conductive input electrode having a plurality of holes extending completely therethrough, said input electrode being fixed relative to said plate inside said envelope in a position such that said input electrode holes lie in registration with said plate holes, a conductive output electrode having a plurality of holes extending completely therethrough, said output electrode being fixed relative to said plate inside said envelope in a position such that said output electrode holes lie in registration with said plate holes and said input electrode holes.
 1. A television camera-type tube comprising: an evacuated envelope; a target fixed within said envelope at one end thereof; an axially positioned electron gun fixed within said envelope at the other end thereof, said gun being constructed to produce an electron beam to scan said target, said beam returning toward said gun away from said target; a perforated glass plate channeltype electron multiplier positioned adjacent and surrounding said gUn to receive electrons from said return beam; said gun having a frusto-conical, secondary-emissive, electrode surface of angle less than 78* in the path of said return beam directing electrons therefrom toward the input side of said electron multiplier; and a collector fixed within said envelope in a position on the output side of said multiplier to collect electrons therefrom, said collector being positioned on the opposite side of said multiplier from said target, said multiplier including a dielectric plate having a plurality of holes extending completely therethrough from said input side to said output side, said holes being defined by surrounding surfaces, said surfaces having a secondary emission ration greater than unity, a conductive input electrode having a plurality of holes extending completely therethrough, said input electrode being fixed relative to said plate inside said envelope in a position such that said input electrode holes lie in registration with said plate holes, a conductive output electrode having a plurality of holes extending completely therethrough, said output electrode being fixed relative to said plate inside said envelope in a position such that said output electrode holes lie in registration with said plate holes and said input electrode holes.
 2. The invention as defined in claim 1, wherein said envelope is substantially cylindrical, said target being disposed perpendicular to the axis of said envelope, said electrode external frusto-conical surface pointing toward said target on the target side thereof and having an axis the same as that of said envelope, the conical surface being inclined at an acute angle of about 45* from said axis, said multiplier having front and rear surfaces parallel to said target, said front surface being closer to said target than said rear surface, said multiplier having a central hole therethrough large in comparison to said perforations, said gun being located in said hole, said frusto-conical surface projecting closer to said target than the said surfaces of said multiplier, said multiplier having first and second electrodes evaporated into said front and rear surfaces, respectively, said collector being a grid parallel to said surfaces spaced from said multiplier electrodes, said collector being positioned adjacent said second electrode, means for maintaining said first and second electrodes and said collector at successively higher potentials, said gun including a cathode, and means for maintaining said cathode at a potential lower than that of said first electrode.
 3. The invention as defined in claim 1, including a photocathode at said one end of said envelope on the side of said target opposite said electron gun, a second channel type electron multiplier between said target and photocathode, and means for deflecting and focusing said electron beam in the plane of said target. 